電界放射形走査電子顕微鏡内疲労試験装置と疲労き裂進展の直接連続観察

概要

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A new servo-controlled electrohydraulic fatigue testing apparatus which can operate in a field-emission scanning electron microscope (Hitachi HFS-2S) was designed. In order to allow direct observation of propagating cracks, piston and cylinder of the testing rig were connected by a link mechanism to move in counter directions so that loading could be applied simultaneously to the both ends of the specimen with arbitrary ratios. Moreover, some electrical means were used to obtain the stroboscopic-image of propagating cracks. Maximum loading capacity of the apparatus is ±5 000 N in tens;ion and compression, with the maximum testing frequency of about 50Hz. Moving seal for high vacuum was made by using metallic bellows, and a turbo-molecular pump in addition to an ion pump was equipped for the vacuum system. Fatigue crack propagation tests were performed on a grain oriented 3% silicon iron at very slow propagation rates. In this range slips were found to occur at a relatively wide region near the crack tip, while in the high propagation rate range it had been reported that alternating slipping-off occurred only at the apex of the crack tip. So the different mechanisms of fatigue crack propagation were suggested for the high and the low ΔK regions for this material.
社団法人日本材料学会の論文
1982-07-15